1. Field of the Invention
The present invention relates to a head recovery device and a head recovery method for recording means provided with a pigment ink discharge port for discharging pigment ink and a dye ink discharge port for discharging dye ink, and an ink jet recording apparatus executing such head recovery.
2. Related Background Art
The recording apparatus having the function of a printer, a copying apparatus or a facsimile machine or employed as the output device for a composite electronic device including a computer or a word processor or for a work station serves to record an image (including a character or a symbol) on a recording material (recording medium) such as paper, fabric, plastic sheet or OHP sheet. Among the various types of recording apparatus, the ink jet system (ink jet recording apparatus) forms a record by discharging ink from recording means (recording head) onto the recording material, and has various advantages, such as easy compactization of the recording means, high-speed recording of a high definition image, recording on plain paper without any particular process, a low running cost, a low noise level because it is a non-impact system, and easy recording of a color image with plural inks (for example color inks).
The energy used for discharging ink from the discharge port of an ink jet recording head can be generated, for example, by an electromechanical converting member such as a piezoelectric element, by irradiation of an electromagnetic wave such as laser light to generate heat thereby discharging an ink droplet, or by an electrothermal converting member including a heat generating resistor for heating liquid. Among these methods, the recording means (recording head) of ink jet type utilizing thermal energy for discharging ink as a droplet is capable of recording at a high resolution because the discharge ports can be arranged at a high density. Among such recording means, a recording head utilizing an electrothermal converting member, or the like, as the energy generating element is advantageous because it can be easily made compact, can fully utilize the advantages of the IC microprocessing technology, which is showing remarkable progress in the semiconductor area and in reliability, and also can be realized in a high density with a low manufacturing cost.
Also there are various requirements for the quality of the recording media, and developments have recently been made for meeting such requirements so that there have been developed recording apparatuses that utilize not only the ordinary recording media such as paper (including thin paper and processed paper) and thin plastic plate (for example OHP sheet) but also fabric, leather, non-woven cloth and metal.
The recording apparatus can be classified as either a serial type, in which the recording is executed by a main scanning operation in a direction crossing the conveying direction of the recording sheet (recording material), or a line type, in which the recording is executed by a recording head supported in a fixed position and having such a length as to cover a predetermined width range (including the entire width) in the transversal direction of the recording sheet. The present invention is applicable to any type of recording apparatus, including the aforementioned recording types. In the ink jet recording apparatus of the above-mentioned serial type, an image is formed on the recording sheet by recording the image (including characters and symbols) by a recording head mounted on a carriage moving along the recording sheet and thereafter conveying the sheet by a predetermined amount (sub scanning).
In the above-described ink jet recording apparatus, an undesirable substance, such as an ink droplet, dust or paper dust, may be deposited on the head face of the recording head during the recording operation, and a cleaning operation of the head face is executed with a cleaning member (for example, wiping or rubbing) in order to eliminate such undesirable substance. Such cleaning member is usually composed of a flexible member, such as a rubber blade, consisting of a rubber-like elastic material.
Also, clogging of the discharge port may result by drying of the ink in the vicinity of the discharge port of the recording head, causing viscosity increase, solidification or deposition of the ink. The clogging of the discharge port may also result from a bubble generated inside the discharge port (flow path) or by dust. In order to recover from (prevent or eliminate) such clogging, there is adopted a suction recovery method of forming a closed system at the ink discharge port portion with a capping member and generating a certain negative suction force at the discharge port face (head face) with a pump, thereby forcedly discharging ink from the discharge port. Also, in order to remove the ink attached to the head face by the suction recovery, there is executed a cleaning (wiping) operation of the head face with a cleaning member.
In the following there will be explained the head recovery device and the heat recovery method of the conventional ink jet recording apparatus with reference to FIGS. 13 and 14. FIG. 13 is a schematic elevation view of a heat recovery device for the conventional ink jet recording apparatus, seen from the front, and FIG. 14 is a schematic lateral view of the heat recovery device shown in FIG. 13, seen from the lateral direction. Referring to FIGS. 13 and 14, there are shown a black head (pigment ink head) 1A for discharging black pigment ink, a color head (dye ink head) 1B for discharging dye inks of different colors (for example cyan, magenta and yellow), a main scanning carriage 2 for positioning and supporting the black head 1A and the color head 1B, and a main scanning rail 3 for guiding and supporting the main scanning carriage 2 in a state capable of reciprocating motion in a direction A which is the recording direction.
There are also shown a rubber cap (for pigment ink head) 4A for forming a closed system (capping) on a discharge port portion 1Aa of the black head 1A, and a rubber cap (for dye ink head) 4B for forming a closed system (capping) on a discharge port portion 1Ba of the color head 1B. These rubber caps 4A, 4B are so positioned and supported by an unrepresented holder member as to be movable by an unrepresented drive source in a capping direction B and in an uncapping direction C, whereby constituted are capping means for the pigment ink head and that for the dye ink head.
Referring to FIGS. 13 and 14, cap absorbing members 9A, 9B for absorbing and retaining ink are provided respectively inside the rubber caps 4A, 4B. Also, in order to prevent solidification and deposition of the inks at the discharge port portions 1Aa, 1Ba by viscosity increase of the inks, preliminary ink discharges are executed from the discharge ports to the cap absorbing members 9A, 9B at predetermined time intervals, even in the course of a recording (printing) operation. There are also provided a suction pump (suction means) 5A for the black head (pigment ink head) and a suction pump (suction means) 5B for the color head (dye ink head). The pumps generate a predetermined suction pressure (negative pressure) at the discharge port portions 1Aa, 1Ba in the capped state, thereby executing a suction recovery operation (recovery process) of forcedly sucking ink from the discharge port portions 1Aa, 1Ba through first tubes 6A, 6B. The pumps discharge the sucked ink into a used ink processing member 8 through second tubes 7A, 7B. There are also provided a cleaning member 10A for the black head (pigment ink head) and a cleaning member 10B for the color head (dye ink head), which are composed of rubber, such as urethane rubber, butyl rubber or silicone rubber, or a porous material, such as sponge.
The cleaning members 10A, 10B are rendered movable in directions D and E by an unrepresented drive source, and, by a movement in the direction D, they come into sliding contact (represented by broken lines) with the head face including the discharge port portions 1Aa, 1Ba to execute a cleaning operation (wiping operation). After the cleaning operation, the cleaning members 10A, 10B further move in a direction D to come into contact with cleaners 111A, 11B (represented by broken lines), whereby the ink droplet, dust, paper dust etc. scraped off from the head face and deposited on the cleaning members 10A, 10B are recovered by transfer to the respectively corresponding cleaners 11A, 11B. In this operation, the caps 4A, 4B of the capping means are moved (retracted) in a direction C by an unrepresented drive source to a position (not shown) not interfering with the cleaning members 10A, 10B of the cleaning means.
In case the ink droplet discharge becomes unstable or impossible, it is necessary to restore the normal ink discharge state by eliminating such failure and the aforementioned recovery means (discharge failure recovery means) is provided as the operation means therefor. As one of such recovery means, there is employed suction recovery means for capping the discharge port of the recording head (for example a recording head cartridge) and applying a negative pressure to the discharge port for example by a suction pump thereby forcedly discharging ink from the recording head. However the recovery means of such negative pressure suction type has been associated with a technical drawback of consuming a large amount of ink for the suction recovery operation.
In order to resolve such technical drawback, there has been proposed, as disclosed for example in the Japanese Patent Application Laid-open No. 2-102058, an ink jet recording apparatus so constructed, upon completion of the recording with the ink jet recording head cartridge, as to discharge a certain amount of the ink droplets from the recording head cartridge and thereafter capping the recording head cartridge (sealing of the discharge port) by pressing a cap thereto.
Also the Japanese Patent Application Laid-Open No. 4-339665 proposes an ink jet recording apparatus so constructed, upon completion of the ink jet recording, as to execute the capping operation after discharging a predetermined amount of the ink droplets into the Interior of the corresponding cap based on the result of detection such as the period in which the recording head cartridge is kept in an open-cap state or the amount of recording.
However, in the conventional head recovery device and head recovery method explained in the foregoing and in the ink jet recording apparatus employing or executing such apparatus or method, though the durability of the various components of the apparatus are not affected in case of dye-based ink (dye ink), the pigment-based ink (pigment ink) shows faster viscosity increase or solidification in comparison with the dye ink and is deposited by such viscosity increase or solidification in the cap absorbing member 9A of the cap 4A for the pigment ink head, whereby the removal of the ink by the aforementioned suction operation may become difficult and the suction ability for the recovery may also be deteriorated. Furthermore the ink is deposited by viscosity increase and solidification at the contact portion of the cap 4A with the pigment ink head 1A to generate a step by the deposited and solidified ink at such contact portion of the cap 4A with the head face, thereby resulting in defective sealing at the capping operation.
Such phenomenon is presumably ascribable to the following. As the pigment-based ink is prepared by dispersing pigment such as carbon black into an aqueous medium, once the aqueous component is evaporated, the pigment particles coagulate and are difficult to dissolve again. Such difficulty in re-dissolution is desirable for the image characteristics but undesirable for the protection of the recording head (recording head cartridge etc.). More specifically, if the pigment-based ink is discharged and remains in the cap for a long time after the recording operation, the pigment ink itself solidifies in the cap and the recovery operation at the re-start of the recording operation cannot realize the stable suction operation whereby it may become difficult to maintain or restore the ink discharging performance of the recording head.